WASHINGTON, April 25 (Reuters) - The U.S. government's costs could increase by $2.3 billion in 2018 if Congress and President Donald Trump decide not to fund Obamacare-related payments to health insurers, according to a study released Tuesday by the Kaiser Family Foundation.

The payments amount to about $7 billion in fiscal year 2017 and help cover out-of-pocket medical costs for low-income Americans who purchase insurance on the individual insurance exchanges created by the Affordable Care Act, often called Obamacare.

Trump has threatened to withhold the payments to force Democrats to the negotiating table on a healthcare bill to replace Obamacare.

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UNITED STATES - MARCH 23: Pro-choice demonstrators including Stephanie Castro, right, and Sandra Sanchez of the National Latina Institute for Reproductive Health, appear outside of the Supreme Court as arguments were heard in a case which religious organizations are challenging the Affordable Care Act's provision that requires employers to cover birth control in health care plans, March 23, 2016. (Photo By Tom Williams/CQ Roll Call)

US President Barack Obama greets attendees after speakin on the Affordable Care Act at the United Community Center in Milwaukee, Wisconsin on March 3, 2016. / AFP / MANDEL NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

Demonstrators opposed to U.S. President Barack Obama's health-care law, Obamacare, hold signs in front of the U.S. Supreme Court in Washington, D.C., U.S., on Wednesday, March 4, 2015. A U.S. Supreme Court argument over Obamacare's tax subsidies divided the justices along ideological lines, potentially leaving two pivotal justices to decide the law's fate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Demonstrators opposed to U.S. President Barack Obama's health-care law, Obamacare, hold signs in front of the U.S. Supreme Court in Washington, D.C., U.S., on Wednesday, March 4, 2015. A U.S. Supreme Court argument over Obamacare's tax subsidies divided the justices along ideological lines, potentially leaving two pivotal justices to decide the law's fate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Representative Steve King, a Republican from Iowa, speaks at the Tea Party Patriots podium in front of the U.S. Supreme Court in Washington, D.C., U.S., on Wednesday, March 4, 2015. A U.S. Supreme Court argument over Obamacare's tax subsidies divided the justices along ideological lines, potentially leaving two pivotal justices to decide the law's fate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Pamela Hurst, center, speaks to the media as her husband Douglas Hurst, a plaintiff in King v. Burwell, right, looks on in front of the U.S. Supreme Court with Michael Carvin, lead attorney for the petitioners and partner at Jones Day, left, in Washington, D.C., U.S., on Wednesday, March 4, 2015. A U.S. Supreme Court argument over Obamacare's tax subsidies divided the justices along ideological lines, potentially leaving two pivotal justices to decide the law's fate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Kathleen Sebelius, former secretary of Health and Human Services (HHS), center, speaks to members of the media in front of the U.S. Supreme Court in Washington, D.C., U.S., on Wednesday, March 4, 2015. A U.S. Supreme Court argument over Obamacare's tax subsidies divided the justices along ideological lines, potentially leaving two pivotal justices to decide the law's fate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Demonstrator Donna Hurlock, a medical doctor from Virginia opposed to U.S. President Barack Obama's health-care law, Obamacare, holds a 'No Obamacare' umbrella in front of the U.S. Supreme Court in Washington, D.C., U.S., on Wednesday, March 4, 2015. A U.S. Supreme Court argument over Obamacare's tax subsidies divided the justices along ideological lines, potentially leaving two pivotal justices to decide the law's fate. Photographer: Andrew Harrer/Bloomberg via Getty Images

UNITED STATES - MARCH 04: Rep. Louie Gohmert, R-Texas, speaks at a rally outside of the Supreme Court during arguments in the King v. Burwell case which deals with tax credits in the Affordable Care Act, March 4, 2015. (Photo By Tom Williams/CQ Roll Call)

UNITED STATES - MARCH 04: Rep. Louie Gohmert, R-Texas, speaks at a rally outside of the Supreme Court during arguments in the King v. Burwell case which deals with tax credits in the Affordable Care Act, March 4, 2015. (Photo By Tom Williams/CQ Roll Call)

Demonstrator Nell Robinson, a medical student from George Washington University, holds a sign in favor of to U.S. President Barack Obama's health-care law, Obamacare, in front of the U.S. Supreme Court in Washington, D.C., U.S., on Wednesday, March 4, 2015. A U.S. Supreme Court argument over Obamacare's tax subsidies divided the justices along ideological lines, potentially leaving two pivotal justices to decide the law's fate. Photographer: Andrew Harrer/Bloomberg via Getty Images

Demonstrator Elodie Huttner holds a sign in support of U.S. President Barack Obama's health-care law, Obamacare, in front of the U.S. Supreme Court in Washington, D.C., U.S., on Wednesday, March 4, 2015. A U.S. Supreme Court argument over Obamacare's tax subsidies divided the justices along ideological lines, potentially leaving two pivotal justices to decide the law's fate. Photographer: Andrew Harrer/Bloomberg via Getty Images

This image taken March 31, 2014 in Washington, DC shows the home page for the HealthCare.gov internet site. Today is the deadline day for uninsured Americans to sign up for coverage through US President Barack Obama's signature healthcare law, the Affordable Care Act. (KAREN BLEIER/AFP/Getty Images)

UNITED STATES - JULY 16: Nicholas Diebel, 14, son of Chairman Pete Sessions, R-Texas, sits at the dais before a House Rules Committee hearing in the Capitol, July 16, 2014, on the constitutionality of a House Republican led lawsuit against President Obama for allegedly overstepping his authority with certain provisions in his health care law. (Photo By Tom Williams/CQ Roll Call)

UNITED STATES - JULY 10: Sen. Mark Udall, D-Colo., conducts a news conference in the Capitol's Senate studio, July 10, 2014, on legislation regarding the Supreme Court decision to allow employers to opt out of the contraception mandate in the Affordable Care Act. (Photo By Tom Williams/CQ Roll Call)

Activists opposed the Affordable Care Act's employer contraceptive mandate celebrate outside of the U.S. Supreme Court in Washington, D.C., U.S., on Monday, June 30, 2014. The Supreme Court dealt a blow to President Barack Obama's health-care law, ruling that closely held companies can claim a religious exemption from the requirement that they offer birth-control coverage in their worker health plans. (Pete Marovich/Bloomberg via Getty Images)

Activists who support the Affordable Care Act's employer contraceptive mandate hold signs outside of the U.S. Supreme Court in Washington, D.C., U.S., on Monday, June 30, 2014. The Supreme Court dealt a blow to President Barack Obama's health-care law, ruling that closely held companies can claim a religious exemption from the requirement that they offer birth-control coverage in their worker health plans. (Pete Marovich/Bloomberg via Getty Images)

Activists who support the Affordable Care Act's employer contraceptive mandate demonstrate outside of the U.S. Supreme Court in Washington, D.C., U.S., on Monday, June 30, 2014. The Supreme Court dealt a blow to President Barack Obama's health-care law, ruling that closely held companies can claim a religious exemption from the requirement that they offer birth-control coverage in their worker health plans. (Pete Marovich/Bloomberg via Getty Images)

Anti-abortion demonstrators hold signs during a Priests for Life protest outside the US Court of Appeals for the DC Circuit Court as the Court hears the oral arguments in the 'Priests for Life v. US Department of Health and Human Services (HHS)' case in Washington, DC, on May 8, 2014. The case centers around the HHS mandate in the Affordable Care Act, known as Obamacare, that religious organizations must cover contraceptions and abortion as part of their health insurance benefits, even if that goes against the organization's religious beliefs. (SAUL LOEB/AFP/Getty Images)

Anti-abortion demonstrators hold signs during a Priests for Life protest outside the US Court of Appeals for the DC Circuit Court as the Court hears the oral arguments in the 'Priests for Life v. US Department of Health and Human Services (HHS)' case in Washington, DC, on May 8, 2014. The case centers around the HHS mandate in the Affordable Care Act, known as Obamacare, that religious organizations must cover contraceptions and abortion as part of their health insurance benefits, even if that goes against the organization's religious beliefs. (SAUL LOEB/AFP/Getty Images)

HOLLYWOOD, FL - APRIL 15: Felue Chang who is newly insured under an insurance plan through the Affordable Care Act receives a checkup from Dr. Peria Del Pino-White at the South Broward Community Health Services clinic on April 15, 2014 in Hollywood, Florida. A report released by the Congressional Budget Office indicates that the Affordable Care Act will cost $5 billion less than originally projected for 2014. (Photo by Joe Raedle/Getty Images)

US President Barack Obama speaks about the Affordable Care Act, also known as Obamacare, with Vice President Joe Biden (R) in the Rose Garden at the White House in Washington on April 1, 2014. Hundreds of thousands of Americans rushed to buy Obama's new health insurance plans on March 31, prompting a victory lap from a White House that paid a steep political price for its greatest achievement. The scramble to sign up under Obama's health care law at the end of a six-month enrollment window caused website glitches and long lines at on-the-spot enrollment centers. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

MIAMI, FL - MARCH 31: Norma Licciardello sits with an agent from Sunshine Life and Health Advisors as they wait for the Affordable Care Act website to come back on line as she tries to purchases a health insurance plan at a store setup in the Mall of Americas on March 31, 2014 in Miami, Florida. Today is the last day for the first yearly sign-up period and Sunshine Life and Health saw a wait of four hours or more for people to see a health insurance advisor. (Photo by Joe Raedle/Getty Images)

MIAMI, FL - MARCH 31: Norma Licciardello sits with an agent from Sunshine Life and Health Advisors as they wait for the Affordable Care Act website to come back on line as she tries to purchases a health insurance plan at a store setup in the Mall of Americas on March 31, 2014 in Miami, Florida. Today is the last day for the first yearly sign-up period and Sunshine Life and Health saw a wait of four hours or more for people to see a health insurance advisor. (Photo by Joe Raedle/Getty Images)

MIAMI, FL - MARCH 31: Jose Villanueva (L) and Doraisy Avila sit with an agent from Sunshine Life and Health Advisors as they look at a pricing plan available from the Affordable Care Act at a store setup in the Mall of Americas on March 31, 2014 in Miami, Florida. Today is the last day for the first yearly sign-up period and Sunshine Life and Health saw a wait of four hours or more for people to see a health insurance advisor. (Photo by Joe Raedle/Getty Images)

MIAMI, FL - MARCH 31: People stand in the line to register to meet with Sunshine Life and Health Advisors that are selling insurance under the Affordable Care Act at a store setup in the Mall of Americas on March 31, 2014 in Miami, Florida. Today is the last day for the first yearly sign-up period and Sunshine Life and Health saw a wait of four hours or more for people to see a health insurance advisor. (Photo by Joe Raedle/Getty Images)

MIAMI, FL - MARCH 31: Andres Cuartas (L) sits with Mercedes Mujica an agent with Sunshine Life and Health Advisors as he purchases a health insurance plan under the Affordable Care Act at a store setup in the Mall of Americas on March 31, 2014 in Miami, Florida. Today is the last day for the first yearly sign-up period and Sunshine Life and Health saw a wait of four hours or more for people to see a health insurance advisor. (Photo by Joe Raedle/Getty Images)

This image taken March 31, 2014 in Washington, DC shows the home page for the White House site indicating the amount of time remaining before open enrollment for the Affordable Care Act closes. Today is the deadline day for uninsured Americans to sign up for coverage through US President Barack Obama's signature healthcare law, the Affordable Care Act. AFP PHOTO / Karen BLEIER (Photo credit should read KAREN BLEIER/AFP/Getty Images)

A Choose Health Delaware sign stands outside an Affordable Care Act enrollment event in Milford, Delaware, U.S., on Thursday, March 27, 2014. Six million Americans have signed up for private health plans under Obamacare, President Barack Obama said, a symbolic milestone for a government that has struggled to get the law off the ground. Photographer: Andrew Harrer/Bloomberg via Getty Images

Marketplace guide Jim Prim works on the Healthcare.gov federal enrollment website as he helps a resident sign up for a health insurance plan under the Affordable Care Act at an enrollment event in Milford, Delaware, U.S., on Thursday, March 27, 2014. Six million Americans have signed up for private health plans under Obamacare, President Barack Obama said, a symbolic milestone for a government that has struggled to get the law off the ground. Photographer: Andrew Harrer/Bloomberg via Getty Images

A Health Insurance Marketplace application checklist hangs at a Westside Family Healthcare center during an Affordable Care Act enrollment event in Bear, Delaware, U.S., on Thursday, March 27, 2014. Six million Americans have signed up for private health plans under Obamacare, President Barack Obama said, a symbolic milestone for a government that has struggled to get the law off the ground. Photographer: Andrew Harrer/Bloomberg via Getty Images

Certified application counselor Tina Gaffney helps a resident create an account for a health insurance plan under the Affordable Care Act at a Westside Family Healthcare center enrollment event in Bear, Delaware, U.S., on Thursday, March 27, 2014. Six million Americans have signed up for private health plans under Obamacare, President Barack Obama said, a symbolic milestone for a government that has struggled to get the law off the ground. Photographer: Andrew Harrer/Bloomberg via Getty Images

Marketplace guide Stephanie Cantres helps a resident sign up for a health insurance plan under the Affordable Care Act at a Westside Family Healthcare center enrollment event in Bear, Delaware, U.S., on Thursday, March 27, 2014. Six million Americans have signed up for private health plans under Obamacare, President Barack Obama said, a symbolic milestone for a government that has struggled to get the law off the ground. Photographer: Andrew Harrer/Bloomberg via Getty Images

MIAMI, FL - MARCH 20: Raquel Martinez, Maria Celia Escalona, Flora Motell and Armando Mesa (L-R) wait for their names to be called to speak with an insurance agent from Sunshine Life and Health Advisors as they and others try to purchase health insurance under the Affordable Care Act at a store setup in the Mall of Americas on March 20, 2014 in Miami, Florida. The owner of Sunshine Life and Health Advisors, Odalys Arevalo, said she has seen a surge in people, some waiting up to 3 hours or more in line, trying to sign up for the Affordable Care Act before the open enrollment period for individual insurance ends on March 31. (Photo by Joe Raedle/Getty Images)

MIAMI, FL - FEBRUARY 13: Hisham Uadadeh walks out of Leading Insurance Agency after enrolling in a health insurance plan under the Affordable Care Act on February 13, 2014 in Miami, Florida. Numbers released by the government showed that about 3.3 million people signed up for health insurance plans under the Affordable Care Act through the end of January. (Photo by Joe Raedle/Getty Images)

MIAMI, FL - FEBRUARY 13: Hisham Uadadeh enrolls in a health insurance plan under the Affordable Care Act with the help of A. Michael Khoury at Leading Insurance Agency on February 13, 2014 in Miami, Florida. Numbers released by the government showed that about 3.3 million people signed up for health insurance plans under the Affordable Care Act through the end of January. (Photo by Joe Raedle/Getty Images)

US Representative Greg Walden, Republican of Oregon and chairman of the National Republican Congressional Committee, speaks during a press conference about healthcare and the Affordable Care Act, known as Obamacare, at the Republican National Committee in Washington, DC, January 28, 2014. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)

JACKSON, KY - JANUARY, 22: Dr. Derrick Hamilton listens to Breathitt County resident Mary Blair's heartbeat during her appointment at the Breathitt County Family Health Center on Tuesday, January 21, 2014 in Jackson, Ky. Despite suffering from a past heart attack and diabetes Blair was able to receive medical coverage through Medicaid expansion under the Affordable Care Act.
(Photo by Luke Sharrett/For The Washington Post via Getty Images)
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LOS ANGELES, CA - JANUARY 20: Supporters of the Affordable Care Act (ACA) march in the 29th annual Kingdom Day Parade on January 20, 2014 in Los Angeles, California. The Kingdom Day Parade honors the memory of African-American civil rights leader Martin Luther King Jr. and coincides with Martin Luther King Day. (Photo by David McNew/Getty Images)

MIAMI, FL - JANUARY 15: As people stand in line to speak with an insurance agent Dailem Delombard sits with an agent from Sunshine Life and Health Advisors as she tries to purchase health insurance under the Affordable Care Act at the kiosk setup at the Mall of Americas on January 15, 2014 in Miami, Florida. Today is deadline day for those that want insurance to start on February the 1st. According to the owner of Sunshine Life and Health Advisors, Odalys Arevalo, their business selling insurance under the Affordable Care Act has exploded so much so that by the end of the week they will be moving to a 24,000 square foot space at the mall because they have outgrown the kiosk. They have over 25 agents and are seeing hundreds of people daily, last Saturday they saw about 1,000 people with wait times of over 5 hours. (Photo by Joe Raedle/Getty Images)

A woman holding a sign in support of the Affordable Care Act is seen as US President Barack Obama's motorcade returns to his vacation compound from the gym at Marine Corps Base Hawaii on December 29, 2013 in Kaneohe Bay, Hawaii. The first family is in Hawaii for their annual holiday vacation. AFP PHOTO / Kent NISHIMURA (Photo credit should read Kent Nishimura/AFP/Getty Images)

Fliers promoting the Get Covered Illinois health insurance marketplace sit in a box at the Bureau County Health Department offices in Princeton, Illinois, U.S., on Wednesday, Dec. 18, 2013. Todays deadline for Americans to sign up for Obamacare health coverage effective Jan. 1 was extended until midnight tomorrow as heavy traffic to the online enrollment system caused a queuing system to be activated Photographer: Daniel Acker/Bloomberg via Getty Images

Samantha Guzman, an Affordable Care Act navigator with the Bureau and Putnam County Health Department, center, assists Jackie Karns as she shops for health insurance at the Bureau County Health Department offices in Princeton, Illinois, U.S., on Wednesday, Dec. 18, 2013. Todays deadline for Americans to sign up for Obamacare health coverage effective Jan. 1 was extended until midnight tomorrow as heavy traffic to the online enrollment system caused a queuing system to be activated Photographer: Daniel Acker/Bloomberg via Getty Images

MIAMI, FL - DECEMBER 11: Susana Hernandez (L) speaks with Rosaly Hernandez, an insurance agent with Sunshine Life and Health Advisors, about purchasing insurance under the Affordable Care Act at a kiosk setup at the Mall of Americas on December 11, 2013 in Miami, Florida. As Health and Human Services Secretary Kathleen Sebelius tesified in Washington, DC before a congressional panel that the Affordable Care Act website was improving, the Sunshine Life and Health Advisors said, that they are starting to see a steady increase in the numbers of people coming to them to purchase and understand the policies offered under the Affordable Care Act. (Photo by Joe Raedle/Getty Images)

Enrollee Douglas Sparks waits to speak to a health navigator at a health insurance education and enrollment event in Silver Spring, Maryland, U.S., on Saturday, Dec. 7, 2013. Government-run health insurance exchanges are at the core of the Patient Protection and Affordable Care Act of 2010 known as Obamacare that seeks to provide access to health coverage for many of the country's estimated 48 million uninsured. Photographer: Andrew Harrer/Bloomberg via Getty Images

Copies of the application for the Health Insurance Marketplace from the Department of Health and Human Services (HHS) are arranged for a in Washington, D.C., U.S., on Friday, Dec. 6, 2013. The health-care website's improved performance has both U.S. political parties shifting strategies, with President Barack Obama's team preparing a January advertising blitz and a wave of celebrity promotions to boost enrollment, allies said. Photographer: Andrew Harrer/Bloomberg via Getty Images

An affordable health coverage sign stands a health insurance education and enrollment event in Silver Spring, Maryland, U.S., on Saturday, Dec. 7, 2013. Government-run health insurance exchanges are at the core of the Patient Protection and Affordable Care Act of 2010 known as Obamacare that seeks to provide access to health coverage for many of the country's estimated 48 million uninsured. Photographer: Andrew Harrer/Bloomberg via Getty Images

HIALEAH, FL - NOVEMBER 14: Venita Mendez works with Gisselle Rubio, an insurance agent with Sunshine Life and Health Advisors, as she looks to purchase an insurance policy under the Affordable Care Act at the store setup in the Westland Mall on November 14, 2013 in Hialeah, Florida. As the insurance agents continue to help people purchase and understand the policies offered under the Affordable Care Act, U.S. President Barack Obama announced that Americans who have had their health insurance plans canceled because of the Affordable Care Act can keep those plans for another year if they wish to. (Photo by Joe Raedle/Getty Images)

The Healthcare.gov website is displayed on a laptop computer arranged for a photograph in Washington, D.C., U.S., on Monday, Nov. 4, 2013. The race to construct an online insurance exchange by Oct. 1 spurred the Obama administration to use an expedited bidding system that limited its choice of a builder to just four companies, including CGI Group Inc. Photographer: Andrew Harrer/Bloomberg via Getty Images

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He has also said he will fund the subsidies if Democrats agree to funding for his proposed border wall with Mexico as part of efforts to pass a government funding bill this week and avert a shutdown. Democrats have rejected the conditional offer.

If no deal is made, parts of the federal government will shut down at 12:01 am (0401 GMT) on Saturday.

The payments are the subject of a pending Republican lawsuit that was appealed by the Obama administration and put on hold when Trump took office.

The government could save $10 billion by revoking the payments, Kaiser said. But insurers that remain in the market would have to hike premiums nearly 20 percent to cover their losses, Kaiser found, so the government would have to spend $12.3 billion on tax credits to help pay for Americans' premium costs - a net increase of 23 percent on federal spending on marketplace subsidies.

The projection assumes that insurers remain in the marketplace next year. Health policy experts have said without the payments, many insurers could not afford to stay in the market and will likely exit, which would leave some U.S. counties without an insurer.

Aetna, UnitedHealth Group Inc and Humana have already exited most state exchanges for 2017 and said they will do so next year as well.